App Engine 1.6.5 Released

[Marzia Niccolai]

Hi,

We've released 1.6.5 today, with some really cool features you can read about here: http://googleappengine.blogspot.com/2012/04/app-engine-165-released.html

One of the most exciting is projection queries, the description of which I'll crib from the above post:

"We’ve introduced an experimental type of query, projection queries, in the Datastore. For the SQL fans amongst us, this is similar to queries of the form:

SELECT Property1, Property2 FROM MyEntity ORDER BY Property3

Projection queries have the same cost and performance characteristics as keys-only queries but return entity objects populated only with the requested properties."

Python docs:

https://developers.google.com/appengine/docs/python/datastore/queries#Query_Projection

Java docs:

https://developers.google.com/appengine/docs/java/datastore/queries#Query_Projection

Enjoy!
-Marzia

[Sun Jing]

I tried to use projection queries:

class Article(db.Model):

title = db.StringProperty(required=True)

# others...

print db.Query('Article', projection=('title')).get()

Traceback (most recent call last):
  File "/base/python_runtime/python_lib/versions/1/google/appengine/ext/admin/__init__.py", line 331, in post
    exec(compiled_code, globals())
  File "<string>", line 3, in <module>
  File "/base/python_runtime/python_lib/versions/1/google/appengine/ext/db/__init__.py", line 2098, in get
    results = self.run(limit=1, **kwargs)
  File "/base/python_runtime/python_lib/versions/1/google/appengine/ext/db/__init__.py", line 2061, in run
    raw_query = self._get_query()
  File "/base/python_runtime/python_lib/versions/1/google/appengine/ext/db/__init__.py", line 2446, in _get_query
    kind = self._model_class.kind()
AttributeError: 'str' object has no attribute 'kind'

print db.GqlQuery("SELECT title FROM Article").get().title

# this one works

[Alfred Fuller]

('title') is not a tuple, you need to use ('title',) or ['title'] instead

>>> print ('title')

title

>>> print ('title',)

('title',)

>>> 

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[Alfred Fuller]

Oh, also db.Query takes a class not a string, should be:

db.Query(Article, projection=('title',)).get() 

[Sun Jing]

Thank you, Alfred.

Can I change projection if I use Model.all() to create a Query object?

[Alfred Fuller]

You can pass the projection in as a keyword argument to any of the query functions:

Article.all().run/fetch/get(projection=('title',))

[Sun Jing]

Thank you, it works. I think the document should be updated:

https://developers.google.com/appengine/docs/python/datastore/queryclass#Query_get

[Alfred Fuller]

I agree :-), the doc update is in progress.

On Tue, Apr 24, 2012 at 10:41 PM, Sun Jing <kea...@gmail.com> wrote:

Thank you, it works. I think the document should be updated:

https://developers.google.com/appengine/docs/python/datastore/queryclass#Query_get

--

[Gopal Patel]

does ndb supports projection query ?

[Ian Marshall]

As a Java person, am I correct to restrain my enthusiasm and wait for
the 1.6.5.1 Java release?


On Apr 24, 10:34 pm, Marzia Niccolai <marce+appeng...@google.com>
wrote:

> Hi,
>
> We've released 1.6.5 today, with some really cool features you can read
> about here:http://googleappengine.blogspot.com/2012/04/app-engine-165-released.html
>
> One of the most exciting is projection queries, the description of which
> I'll crib from the above post:
>
> "We’ve introduced an experimental type of query, projection queries, in the
> Datastore. For the SQL fans amongst us, this is similar to queries of the
> form:
>
> SELECT Property1, Property2 FROM MyEntity ORDER BY Property3
>
> Projection queries have the same cost and performance characteristics as
> keys-only queries but return entity objects populated only with the
> requested properties."
>

> Python docs:https://developers.google.com/appengine/docs/python/datastore/queries...
>
> Java docs:https://developers.google.com/appengine/docs/java/datastore/queries#Q...
>
> Enjoy!
> -Marzia

[Maxim Lacrima]

Does this release include a fix for this issue:

http://code.google.com/p/googleappengine/issues/detail?id=6820

I still have problems described there if I do large asynchronous puts.

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with regards,
Maxim

[pdknsk]

When using projection queries for just a single property, does this
also return keys? The answer is probably yes, as returned items can
probably not be key-less, or can they?

[Alfred Fuller]

Projection queries return the properties you projected and key for each entity that matches the query.

[Ron Wilhelm]

GQL on ndb models supports projection queries.

-Ron

On Apr 25, 2:23 am, Gopal Patel <patelgo...@gmail.com> wrote:
> does ndb supports projection query ?
>
>
>
>
>
>
>
> On Wed, Apr 25, 2012 at 11:43 AM, Alfred Fuller <arful...@google.com> wrote:
> > I agree :-), the doc update is in progress.
>
> > On Tue, Apr 24, 2012 at 10:41 PM, Sun Jing <kea...@gmail.com> wrote:
>
> >> Thank you, it works. I think the document should be updated:
>

> >>https://developers.google.com/appengine/docs/python/datastore/querycl...

[Alfred Fuller]

ndb does not yet officially support projection queries, so there might be some rough edges if you use them.

[Warwick Allison]

Projection queries do not seem to work for properties that are
db.ReferenceProperty(). So for example, this works:

SELECT * FROM Person

result.mother.name + " is the mother of " + result.name

but this does not:

SELECT name,mother,father FROM Person

Is this just an oversight, or an undocumented permanent limitation?
(if the former, I'll wait, if the latter I may redesign my db to not
use ReferenceProperty just to see what the performance improvement is
like!).

(no, I don't actually have a Person database, this is an example ;-)

[Emanuele Ziglioli]

Sources on SVN have been updated too, thank you!
http://code.google.com/p/googleappengine/source/browse/

Interesting features ahead:
http://www.google.com/url?sa=D&q=http://code.google.com/p/googleappengine/source/browse/trunk/java/src/main/com/google/appengine/api/socket/&usg=AFQjCNES0GWahEiGl-QyGx2AMILX_n0dBA